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<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
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<body>
  <script>
    //10. 检测是否是2到4位汉字
    let str = prompt("请输入内容");
    let reg = /^[\u4e00-\u9fa5]{2,4}$/;
    if(reg.test(str)){
          alert("true");
    }else{
        alert("false");
    }
  </script>
</body>
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